Conventionally, a method has been known that refers to identification information included in received data, and determines the process on the received data. This method has a problem of being inapplicable if a communication layer on which an encrypting (decrypting) process is performed is different from a communication layer on which the process on the received data is determined.
Another method has also been known that determines the content of a process on received data on the basis of a MAC address or an IPv6 address. Unfortunately, each address can be spoofed, this method has a security problem in the case of use for a smart meter.